1. Technical Field
This invention generally relates to semiconductor circuit fabrication, and more specifically relates to programming structures in semiconductor devices.
2. Background Art
The proliferation of electronics in our modern world is in large part due to integrated circuit semiconductor devices. Integrated semiconductor devices are designed and used for widely differing applications. For this reason it is often beneficial to have the ability to "personalize" a semiconductor device during fabrication. For example, many large scale integrated circuits use built in redundancy as a method of improving fabrication yield. In a device such as a dynamic random access memory (DRAM) fuse links are a well known redundancy technique. The fuse links are used to access spare bit lines and/or word lines to increase yield. Typically, the semiconductor device is built and then tested. Some types of flaws in the device, such as bad bit lines in a DRAM, can be bypassed by blowing an appropriate fuse link which disconnects the defective circuit.
Device customization is another reason to personalize a semiconductor circuit. Customization involves changing the structure of the semiconductor device to meet specific needs. Often, it is not cost effective to create separate fabrication lines, with different masks and such, for each small change in the device. For this reason, specific customization techniques are used to personalize the device, i.e., to make specific changes in the device to meet a particular need. Some customization techniques use fuse links to customize a device for a particular need. For this, some of the available fuses are blown by a laser or other means to make customized changes to the device.
Unfortunately, the use of fuse links for device personalization has inherent limitations. Specifically, the fuse link can only be blown open or left closed. The fuse link cannot be used to make a previously open circuit closed. In particular, fuse links can only be used to open a selected circuit; they cannot be used to connect conductors in the device. This limits the type of personalization that can be easily accomplished. For this reason, the use of fuse links in semiconductor personalization is limited.
Therefore, there existed a need to provide an improved structure and method for semiconductor device personalization. Specifically a need existed for a structure and method that allows circuit connections to be made as part of a device personalization.